If a loan has a debit balance , it means that we have given loan to someone, and for which we will recieve interest.
Nasically it has a debit balance because of the following:
firstly, loan is part of real account and according to it what goes out is debited.........so here also we are giving loan so it is to be debited.........
so this is the reason that it is debited............
Now, loan (Dr.) is treated as an asset because for us it is an investment for which we will receive a regular interest.....
So, the above mentioned are the reasons that we treat LOAN(Dr.) as an asset.....
Hope that this answer would be helpful for you !!!!!!!